There is a scripting interface to the generation of map averages. As above, the maps need not be on the same grid or in the same space group. The resulting map will have the same gridding and space group as the first map in the list. Typical usage:
(average-map '((1 1.0) (2 1.0))))
The argument to (average-map is a list of lists, each list
element is a list of the map number and a weighting factor (1.0 in this
case).